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Identify discontinuities for the following function as either a jump or a removable discontinuity : f(x) = x2-10x+21x-7

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प्रश्न

Identify discontinuities for the following function as either a jump or a removable discontinuity :

f(x) = `(x^2 - 10x + 21)/(x - 7)`

बेरीज
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उत्तर

Given, f(x) = `(x^2 - 10x + 21)/(x - 7)`

It is rational function and is discontinuous if

x – 7 = 0 i.e., x = 7

∴ f(x) is continuous for all x ∈ R, except at x = 7.

∴ f(7) is not defined.

Now, `lim_(x -> 7) "f"(x) =  lim_(x -> 7) (x^2 - 10x + 21)/(x - 7)`

= `lim_(x -> 7) ((x - 7)(x - 3))/(x - 7)`

= `lim_(x -> 7) (x - 3)  ...[(because x -> 7","  therefore x ≠ 7),(therefore x - 7 ≠ 0)]`

= 7 – 3

= 4

Thus `lim_(x -> ) "f"(x)` exist but f(7) is not defined

∴ f(x) has a removable discontinuity.

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पाठ 8: Continuity - EXERCISE 8.1 [पृष्ठ १७३]

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